The invention relates to a rotary combustion engine comprising a non-rotary outer casing; a non-rotary inner casing; a power shaft provided with an eccentric part; a driving eccentric ring provided between the outer casing and the inner casing and mounted in bearings on the eccentric part of the power shaft; a combustion chamber arrangement for burning a mixture of fuel and air supplied into the engine between the eccentric ring and the inner casing such that the eccentric ring drives the power shaft by means of substantially non-rotating eccentric movement; divider members for dividing the combustion chamber arrangement into at least two parts of equal size, whereby the divider members extend through the inner casing and are in close contact with an inner surface of the driving eccentric ring; an eccentric device or control for driving the divider members back and forth with respect to the inner casing, whereby the eccentricity of the eccentric device or control corresponds with the eccentricity of the eccentric part of the power shaft.
The invention also relates to a hydraulic motor, whereby in the above-described arrangement, in place of the combustion chamber arrangement, a pressure chamber arrangement is provided between the eccentric ring and the inner casing for conveying hydraulic fluid thereto and therefrom.
Such an engine and motor are known from Finnish Patents No. 110807 and 114235.
A problem with the solutions described in these patents is that the distance between the sealing surface of the divider members and the inner surface of the driving, i.e. the first, eccentric ring does not remain constant, owing to the paths of the system. This is because the divider members are slightly inclined towards their matching surfaces for the most of the time; they are perpendicular, i.e. radially oriented, with respect to the eccentric rings guiding them at a given time only when they are in line with a line passing through the central axis of the power shaft and the centre of eccentricity of the eccentric ring arrangement.